Epitope mapping of salmonella flagellar hook-associated protein, FlgK, with mass spectrometry-based immuno-capture proteomics using chicken (gallus gallus domesticus] sera

Authors: Yeh, Hung-Yueh; KOJIMA, KYOKO - University Of Alabama; MOBLEY, JAMES - University Of Alabama

Submitted to: Veterinary Immunology and Immunopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/13/2018
Publication Date: 7/1/2018
Citation: Yeh, H., Kojima, K., Mobley, J.A. 2018. Epitope mapping of salmonella flagellar hook-associated protein, FlgK, with mass spectrometry-based immuno-capture proteomics using chicken (gallus gallus domesticus] sera. Veterinary Immunology and Immunopathology. 201:20-25. https://doi.org/10.1016/j.vetimm.2018.05.006.
DOI: https://doi.org/10.1016/j.vetimm.2018.05.006

Interpretive Summary: Salmonella is an important foodborne pathogen, which causes human acute bacterial gastroenteritis worldwide. Poultry products are considered as the major source of this bacterium for human infection. To prevent human infection, vaccination of chickens is one of powerful means to reduce this bacterium in broiler chicken gut and minimize contamination in poultry. The flagellar hook associated protein (FlgK) has been implicated for microorganism colonization in the host gastrointestinal tract as well as inducing protective antibodies. In this report, we determined linear immunoreactive sequences on FlgK using mass spectrometry in conjunction with broiler sera. The results showed (1) the FlgK proteins are highly conserved among Salmonella serovars, (2) the rFlgK protein was produced by the recombinant technique, and was able to induce immune response in chickens, and (3) four peptides on the rFlgK protein were captured by sera from chickens immunized with the rFlgK protein. These four peptides were also reacted to 64 individual serum samples collected from 44 - 52 weeks old chickens, suggesting that these peptides may represent the shared immunodominant sequences on the FlgK protein. The findings of the specific shared linear immunodominant sequences in this study provide a rationale for further evaluation to determine their uses as subunit vaccines covering multiple serotypes for chicken immunization, and subsequently, for providing safer poultry products for human consumption.

Technical Abstract: Salmonella, a Gram-negative rod, is the leading foodborne pathogen associated with human acute bacterial gastroenteritis worldwide. The Salmonella flagellum is responsible for bacterial movement, colonization and invasion in the host gastrointestinal tract. The flagellum has a complex structure, composed of more than 35 proteins. Among them, we were interested in the flagellar hook-associated protein (FlgK), which is an immunodominant protein in chickens. In this communication, we applied mass spectrometry-based proteomics in conjunction with chicken immunized sera to map the linear immunoepitopes in the FlgK protein, validated the epitopes with peptide ELISA, and determined serum reactivity to the epitopes from commercial chickens. We demonstrated the FlgK proteins are highly conserved among Salmonella serovars. The rFlgK protein was produced by the recombinant technique, and was able to induce immune response in chickens. Further, this study identified four peptides (AEG, GAQ, TAD and LEI) in the rFlgK protein that were captured by sera from chickens immunized with the rFlgK protein. These four peptides were also reacted to 64 individual serum samples collected from 44 - 52 weeks old chickens, suggesting that these peptides may represent the shared immunodominant epitopes on the FlgK protein. The findings of the specific shared linear immunodominant epitopes on the FlgK protein in this study provide a rationale for further evaluation to determine their utility as epitope vaccines covering multiple serotypes for chicken immunization, and subsequently, for providing safer poultry products for human consumption.